Human granulocytic ehrlichiosis (HGE) is an illness caused by a rodent bacterium which is generally transmitted to humans by the same tick that is responsible for the transmission of Lyme disease and babesiosis, thereby leading to the possibility of co-infection with Lyme disease, babesiosis and HGE from a single tick bite. The bacterium that causes HGE is believed to be quite widespread in parts of the northeastern United States and has been detected in parts of Europe. While the number of reported cases of HGE infection is increasing rapidly, infection with Ehrlichia including co-infection with Lyme disease, often remains undetected for extended periods of time. HGE is a potentially fatal disease, with the risk of death increasing if appropriate treatment is delayed beyond the first few days after symptoms occur. In contrast, deaths from Lyme disease and babesiosis are relatively rare.
The preferred treatments for HGE, Lyme disease and babesiosis are different, with penicillins, such as doxycycline and amoxicillin, being most effective in treating Lyme disease, anti-malarial drugs being preferred for the treatment of babesiosis and tetracycline being preferred for the treatment of ehrlichiosis. Accurate and early diagnosis of Ehrlichia infection is thus critical but methods currently employed for diagnosis are problematic.
All three tick-borne illnesses share the same flu-like symptoms of muscle aches, fever, headaches and fatigue, thus making clinical diagnosis difficult. Microscopic analysis of blood samples may provide false-negative results when patients are first seen in the clinic. The only tests currently available for the diagnosis of HGE infection are indirect fluorescent antibody staining methods for total immunoglobulins to Ehrlichia causative agents and polymerase chain reaction (PCR) amplification tests. Such methods are time-consuming, labor-intensive and expensive. There thus remains a need in the art for improved methods for the detection of Ehrlichia infection, particularly as related to HGE. The present invention fulfills this need and further provides other related advantages.